Method for controlling permanent magnet synchronous motor

Abstract

A method for controlling a permanent magnet synchronous motor includes detecting an absolute angular position and using the angular position to calculate a rotational speed of the motor; detecting a voltage of a battery as a power source; calculating a compensated speed from a rotational speed of the permanent magnet synchronous motor based on a torque command, the rotational speed of the permanent magnet synchronous motor, and the battery voltage; generating a d-axis current command and a q-axis current command corresponding to the torque command and the compensated speed; calculating a d-axis voltage command and a q-axis voltage command based on the d-axis current command and the q-axis current command; converting the d-axis voltage command and the q-axis voltage command into three-phase voltage commands based on the detected absolute angular position; and controlling the operation of the permanent magnet synchronous motor based on the three-phase voltage commands.

What is claimed is:  
     
       1. A method for controlling a permanent magnet synchronous motor, the method comprising:
 detecting an absolute angular position of a permanent magnet synchronous motor; 
 calculating a rotational speed of the permanent magnet synchronous motor based on the detected absolute angular position; 
 detecting a voltage of a battery as a power source; 
 calculating a compensated speed, for which a battery voltage variation is compensated, from the rotational speed of the permanent magnet synchronous motor based on a torque command, the rotational speed of the permanent magnet synchronous motor, and the battery voltage; 
 generating a d-axis current command and a q-axis current command corresponding to the torque command and the compensated speed using a predetermined current command map; 
 converting three-phase currents flowing into the permanent magnet synchronous motor into a d-axis feedback current and a q-axis feedback current based on the detected absolute angular position; 
 calculating a d-axis voltage command and a q-axis voltage command based on the d-axis current command, the q-axis current command, the d-axis feedback current, and the q-axis feedback current; 
 converting the d-axis voltage command and the q-axis voltage command into three-phase voltage commands based on the detected absolute angular position; and 
 controlling the operation of the permanent magnet synchronous motor based on the three-phase voltage commands, 
 wherein the calculating the compensated speed comprises: 
 determining whether the rotational speed of the permanent magnet synchronous motor is greater than a predetermined weight application speed; 
 calculating an operating weight factor by applying a weight to the rotational speed and the torque command, if the rotational speed of the permanent magnet synchronous motor is greater than the weight application speed; and 
 calculating the compensated speed, for which a battery voltage variation is compensated, from the rotational speed of the permanent magnet synchronous motor based on the operating weight factor and a reference voltage used when the current command map is set. 
 
     
     
       2. The method of  claim 1 , wherein the operating weight factor is calculated by the following equation E1 based on predetermined speed weightweight factor of speed and weight factor of torque command weight:
     K   N   =K   ω (ω rpm −ω 0  )+ K   T   |T   e *|  E1:
 
 wherein KN represents the operating weight factor, Kω represents the speed weightweight factor of speed, ωrpm represents the motor rotational speed, ω 0  represents the weight factor of application start speed, KT represents the weight factor of torque command weight, and Te* represents the torque command. 
 
     
     
       3. The method of  claim 1 , wherein the operating weight factor is zero if the rotational speed of the permanent magnet synchronous motor is smaller than the weight application speed. 
     
     
       4. The method of  claim 1 , wherein the calculation the compensated speed further comprises determining whether the battery voltage is greater than a predetermined compensation starting voltage,
 wherein if the battery voltage is greater than the compensation starting voltage, the compensated speed is calculated and used as an input of the current command map data, and if the battery voltage is smaller than the compensation starting voltage, the rotational speed of the permanent magnet synchronous motor is used as an input of the current command map data instead of the compensated speed. 
 
     
     
       5. The method of  claim 1 , wherein the compensated speed is calculated by a motor speed normalization formula in which the operating weight factor, the battery voltage, and the rotational speed of the permanent magnet synchronous motor are used as input variables. 
     
     
       6. The method of  claim 5 , wherein the compensated speed is a normalized motor speed calculated by the motor speed normalization formula represented by the following equation E2: 
       
         
           
             
               
                 
                   
                     
                       ω 
                       
                         rpm 
                         , 
                         Nom 
                       
                     
                     = 
                     
                       
                         [ 
                         
                           1 
                           + 
                           
                             F 
                             ⁢ 
                             
                               { 
                               
                                 
                                   
                                     ( 
                                     
                                       1 
                                       + 
                                       
                                         K 
                                         N 
                                       
                                     
                                     ) 
                                   
                                   ⁢ 
                                   
                                     
                                       V 
                                       
                                         DC 
                                         , 
                                         MAP 
                                       
                                     
                                     
                                       V 
                                       DC 
                                     
                                   
                                 
                                 - 
                                 1 
                               
                               } 
                             
                           
                         
                         ] 
                       
                       ⁢ 
                       
                         ω 
                         rpm 
                       
                     
                   
                 
                 
                   E2 
                 
               
             
           
         
         wherein ωrpm,Nom represents the normalized motor speed, KN represents the operating weight factor, VDC,MAP represents the reference voltage used when the map is set, VDC represents the battery voltage, and F is equal to 1(VDC≧V0) or 0(VDC<V0), in which, VDC represents the battery voltage and V0 represents the compensation start voltage.